Plasma OLC is elevated in mild experimental uremia but is not associated with hypertension

Background: Little is known about the renal handling of endogenous ouabain- like compound (OLC). The aim of this study was to determine the normal rena l clearance of OLC and the effect of mild experimental uremia on plasma OLC and its clearance. Methods: Male Wistar rats were studied 8 weeks after subtotal (5/6th) nephr ectomy (n = 8), and compared with a control sham-operated group: (n = 8). Results: Plasma creatinine and OLC were higher in uremic animals compared w ith, controls (creatinine 76 +/- 5.6 mu mol/L v 45 +/- 9.61 mu mol/L, respe ctively, P < .00005; OLC 195 +/- 62 pmol/L v 121 +/- 62 pmol/L, P < .02). C reatinine clearance and OLC clearance were lower in uremic animals compared with controls (creatinine 1.06, +/- 0.12 mL/min v 1.58 +/- 0.32 mL/min, re spectively, P < .002; OLC 23.6 +/- 10.4 muL/min v 33.2 +/- 11.4 muL/min, P < .05). There were no significant differences (all P > .05) between the ure mic and control groups in the fractional clearance of OLC (uremic 2.3% +/- 1.0% v control 2.2% +/- 1.0%), OLC excretion rate (uremic 6.2 +/- 2.4 pmol/ 24 h v control 5.0 +/- 1.1 pmol/24 h) or in the mean systolic blood pressur e (BP) (uremic 132 +/- 13 mm Hg v control 126 +/- 3 mm Hg). The amount of O LC excreted per unit of functioning nephron mass was 78% higher in uremic a nimals than in controls. The rate of tubular absorption varied linearly wit h filtered load, did not differ between groups, and showed no evidence of s aturation. Conclusions: The kidneys are an important excretion route for plasma OLC an d moderate but significant increases may occur without inducing hypertensio n in, the short term. The low fractional clearance of OLC is most likely du e to tubular absorption and/or catabolism, Am J Hypertens 200 1; 14:1112-11 15 (C) 2001 American Journal of Hypertension, Ltd.